Many investigators believe that the autonomic nervous system may be involved in hyperactivity (HA) in children. The objectives of our studies are to investigate differences in autonomic functioning between HA and normal children by means of peripheral indicators such as skin conductance, heart rate and pupillary activity, to predict which HA will respond favorably to stimulant drugs, and to assess the effects of the drugs on both autonomic activity and on task performance which depends on attention such as reaction time. The hypothesis that HA and normal children respond diifferently to stimulant drugs has been tested in a study of the effects of d-amphetamine on autonomic activity and attention in 6-13 year-old normal and HA boys. Male adults have been tested on the same protocol to test for age differences in drug effects.